Antihistamines

Your doctor has just prescribed an antihistamine for you. It may be one of the following (list not complete):

Sedative antihistamines

• Buclizine
• Chlorpheniramine
• Cyproheptadine
• Hydroxyzine
• Mebhydrolin
• Promethazine
• Oxatomide

Less-Sedative Antihistamines

• Acrivastine
• Astemizole
• Cetirizine
• Loratadine
• Terfenadine
• Levocetirizine
• Desloratadine

What are antihistamines used for?

Antihistamines are used to relieve itch, redness and swelling in some skin conditions and other types of allergy. They also help to relieve some of the symptoms of the common flu and hay fever, like sneezing, runny nose and watery eyes. They work by cancelling the effects of histamine produced by the body in allergic conditions.

How should I take antihistamines?

• Antihistamines are available in tablets or liquids. Follow the dosage instructions on the label. Do not take more than recommended unless advised by your doctor.
• Take this medicine with some food to reduce stomach irritation if necessary.

What should I do if I forget a dose?

Take the missed dose as soon you remember. If it is almost time for your next dose, do not take the missed dose at all. Resume your regular dosing schedule. Do not take double the dose to make up for the missed one.

What other effects may antihistamines cause?

Certain side effects of this medicine are not unusual and may even disappear during treatment. If any of the following effects persist or are severe, consult your doctor:-

• Some antihistamines may cause some people to feel drowsy, while some antihistamines do not have this effect at all. If you are affected, do not drive, operate machinery or do work that requires you to be alert.
• Blurred vision
• Difficult or painful urination
• Dry mouth (Drink fluids or suck sweets to relieve this).
• Increased appetite (if you are taking cyproheptadine)

What precautions should I take?

• Before taking this medicine, check with your doctor if you are pregnant, intending to conceive or are breast feeding.
• Avoid taking alcohol, sleeping pills, tranquillizers or muscle relaxants with antihistamines, as these tend to add together to make you more drowsy.
• Inform your doctor that you are taking antihistamines before you have any skin tests for allergies. The results of the test may be affected by antihistamines.

How should I store antihistamines?

• Store this medicine away from heat and direct sunlight in a cool, dry place, out of reach of children.
• Do not keep this medicine with other medications in the same container. Keep medicines separately in labelled containers When in doubt, consult your doctor or pharmacist.

Contributors:

Dr Christophe HSU – dermatologist. Geneva, Switzerland

National Skin Centre. Singapore